1. Field of the Invention
The present invention is directed to certain novel labile quaternary ammonium salts characterized as being transient. More particularly, the present invention extends to certain transient derivatives which could be characterized chemically as labile quaternary ammonium salts which exhibit extreme solubility and which protect its components (i.e., tertiary amine, aldehyde and carboxylic acid against oxidation, dealkylation and protonation, and yet, are predictably "cleaved" to release an active moiety and/or moieties.
For purposes of this application, the term "labile" denotes a quaternary ammonium salt of a tertiary (t) aliphatic amine or an aromatic amine which is stable in the neat state, but when placed in an aqueous or alcoholic environment (preferentially slightly basic or acidic), or in biological systems (e.g., serum, blood, liver homogenate) will undergo enzymatic and/or acid or base cleavage, thus releasing the original tertiary aliphatic amine or aromatic amine, or its proton salt.
The term "transient" pertains to a quaternary ammonium salt as described above, which, after chemical and/or enzymatic hydrolysis, will "cleave" into three moieties (tertiary aliphatic amine or an aromatic amine, or a salt thereof, an aldehyde, and a carboxylic acid) in equal molecular amounts. That is, these transient derivatives are adequate for protecting and/or solubilizing tertiary aliphatic amines or aromatic amines, aldehydes and carboxylic acids, prior to their chemical and/or enzymatic release for their intended use. Release occurs in such a manner that a sufficient amount of the compound intended to be delivered is available for its intended use.
For example, in the field of drug chemistry, and specifically, any drug containing a tertiary aliphatic amine or an aromatic amine function as described in the above generic formula, such a drug is transformed into a remarkably more soluble labile quaternary ammonium salt, which after administration is resistant to extensive metabolism at or near the tertiary or aromatic amine function, while the active tertiary or aromatic amine is released following chemical and/or enzymatic hydrolysis at its therapeutic site of action.
2. Description of the Prior Art
One of the basic methods of synthesis of the compounds encompassed within the above-described generic formula consists in reacting a compound of the formula (A) below wherein R and R.sub.1 are defined as above with a compound of the formula (B) below, wherein R, R.sub.1, N and N and X are defined as above: ##STR3##
The compounds of formula (A) above are old in the art and are formed by the reaction between an aldehyde (R -- CHO) and an acyl halide ##STR4## See, R. Adams and E. H. Vollweiler, J. Amer. Chem. Soc., 40, 1732 (1918); H. E. French and R. Adams, ibid., 43, 651 (1921); L. H. Ulich and R. Adams, ibid., 43, 660 (1921).
Thus, preparation of the compounds of formula (A) can be described by reference to the following equation, wherein R and R.sub.1 are defined as above: ##STR5##
The compounds of formula (A) have been used in the past to protect a carboxy function in the following manner: ##STR6##
In the above equation, R and R.sub.1 are defined as above; R.sub.2 represents the residue of ampicillin or a salicyclic acid derivative; and M represents an alkali metal salt (Na, K, etc.). See, "Acyloxymethyl Esters of Ampicillin," W. V. Daehne, E. Fredriksen, E. Gundersen, F. Lund, P. Morch, H. J. Petersen, K. Roholt, L. Tybring, and W. V. Godfredsen, J. Med. Chem., 13, 607 (1970), or British Pat. No. 1,220,457. While those compounds of formula (A) have been used as outlined above, i.e., protecting the carboxy function, this utility has no bearing on the invention disclosed and claimed herein. On the other hand, it is generally known that any activated haloalkyl compound (e.g., benzyl bromide or chloride) will react with a tertiary aliphatic amine to form the corresponding quaternary ammonium salt. However, this salt does not undergo hydrolytic cleavage, which is a necessary characteristic of the labile quaternary ammonium salts of this invention.